Vacuum processing systems for processing 100 mm, 200 mm, 300 mm or other diameter wafers are generally known. Typically, such a vacuum processing system has a centralized transfer chamber mounted on a monolith platform. The transfer chamber is the center of activity for the movement of wafers being processed in the system. Wafers are in the transfer chamber only long enough to be transferred therethrough to another chamber for storing or processing. One or more process chambers attach to the transfer chamber at valves through which wafers are passed by a robot in the transfer chamber. The valves close in order to isolate the process chambers while wafers are being processed therein. Physically, the process chambers are either supported by the transfer chamber and its platform or are supported on their own platform. Inside the system, the transfer chamber is typically held at a constant vacuum; whereas, the process chambers may be pumped to a greater vacuum for performing their respective processes.
Afterward, the process chamber's pressure must be returned to the level in the transfer chamber before opening the valve to permit access between the chambers.
Access to the transfer chamber for wafers from the exterior of the system, or from the manufacturing facility, is typically through one or more load lock chambers. The load lock chambers cycle between the pressure level of the ambient environment and the pressure level in the transfer chamber in order for the wafers to be passed therebetween, so the load lock chambers transition the wafers between the atmospheric pressure of a very clean environment to the vacuum of the transfer chamber.
Some common transfer chambers have facets for four to six process chambers and load lock chambers. For a six-faceted transfer chamber, typically two of the facets are for load lock chambers, and the other four facets are for process chambers. The process chambers include rapid thermal processing (RTP) chambers, physical vapor deposition (PVD) chambers, chemical vapor deposition (CVD) chambers, etch chambers, etc. The productivity of a vacuum processing system is increased when more process chambers are mounted to the transfer chamber, because more wafers can be processed at a given time. Additionally, less; space is required in the manufacturing facility if the productivity of the system is maximized.
Some of the processes performed by the process chambers cause the wafers processed therein to be heated. For some of the processes, the heating is incidental to the process; but for some other processes the heating is a significant part of the process, and for some of these processes, such as RTP, the heating is the process. A process may require that a wafer be cooled before it is placed back into the load lock chamber after processing. For such processes, one or more of the facets of the system mounts a cool-down chamber.
Generally, a cool-down chamber receives a heated wafer from the transfer chamber. The cool-down chamber typically has a plurality of lift pins that lift the wafer off of the blade of the robot, so the blade can be retracted out of the cool-down chamber, and then lowers the wafer onto a cooling plate. The cooling plate is disposed on the bottom of the cool-down chamber, and it is typically water cooled to increase the heat transfer rate. The close proximity of the wafer to the cooling plate permits the wafer to cool by radiating heat from the underside of the wafer to the cooling plate. After a sufficient time to cool the wafer has elapsed, typically a few seconds to a few minutes, the lift pins raise the wafer up again, the robot blade extends under the wafer, the lift pins lower the wafer onto the blade, and the robot removes the wafer from the cool-down chamber and transfers the wafer to a load lock chamber.
Since a cool-down chamber occupies one of the locations on the transfer chamber that could be occupied by a process chamber, the productivity potential, or throughput, of the vacuum processing system is decreased. Therefore, in order for a manufacturing facility to achieve the same throughput as would be achieved if each system had the maximum number of process chambers and no cool-down chambers, the manufacturing facility would have to increase the number of systems in the facility, which translates to an increase in the amount of floor space dedicated to these systems. Thus, the manufacturing costs increase.
A need, therefore, exists for a vacuum processing system that provides for cooling wafers without sacrificing a process chamber or system throughput.